It is known in the audio/video electronics arts to interconnect a variety of consumer electronic processing devices on a bus structure, so that signal available at one device may be utilized by another device connected on the bus. For example audio/video signal available from a television receiver may be applied to a video cassette recorder for storage, or the audio from a television receiver may be applied to a component stereo system for reproduction etc. Examples of this type of audio/video interconnect systems may be found in U.S. Pat. No. 4,575,759; 4,581,664; 4,647,973; and 4,581,645.
The signals distributed in these analog bus systems are relatively self contained. That is they include all the timing information necessary for the respective devices connected to the bus to decode the respective signals.
Currently there are a number of compressed audio and video transmission systems, such as the Grand Alliance HDTV system proposed for terrestrial high definition television broadcasting, or the DirecTV.TM. system which currently broadcasts compressed NTSC signal via satellite. Both systems transmit program material in transport packets, and transport packets for different programs and/or program components may be time division multiplexed in a common frequency band. Respective packets undergo noise detection/correction encoding prior to transmission and after reception, and the transport packets are thereafter reconstituted in a receiver. Recording apparatus (e.g. VCR or video disc) and authoring apparatus (e.g. cameras or camcorders) for compressed signals, on the other hand, may process the compressed signals in the same packet format, however they may not require the same noise processing. As a consequence the conveyance of signal between processing components is most conveniently effected in packet form.
A problem arises in communicating compressed signals between processing components particularly if one of the processing components is a recording device. The problem is that many transport packets of compressed data include no synchronization indicia. In addition, the transport packets may not arrive or be generated at a uniform rate. Recording apparatus, for example, require relatively precise timing for reasons of playback speed variability. That is, compressed data must be precisely located on the recording medium, if the recording device is to include a variety of playback features.